Microbial infections in the mouth are known to play a major role in dental caries, plaque formation, gingival destruction and dental erosion with ultimate involvement of bone and loss of teeth.
Dental caries, that is, damage to the tooth surface or enamel is believed to be primarily caused by the formation of dental plaque on and around teeth. The dental plaque, a product of microbial growth, is a dense microbial layer consisting of a mass of microorganisms embedded in a matrix and accumulating on the teeth and in adjacent surfaces. A wide variety of microorganisms are found in the oral cavity, of which some, particularly certain bacteria such as Streptococcus mutans can produce acids or other toxic substances, which can cause decomposition of tooth enamel. In addition to microorganisms, dental plaque is composed of numerous other substances such as milk, protein, minerals derived from saliva, dead cells, and food residues which may be dissolved or present in particulate form.
Recent dental research suggests that the major potential for harm by dental plaque resides in the bacteria component thereof. Specifically, bacterial metabolism may result in the production of acids, toxins, and enzymes which are deleterious to neighboring oral tissues. Of particular concern is the production of acid which results in a decline in the pH value of the saliva below its normal pH value of 7.0 to 7.5. The amount of the pH decline of the saliva depends upon the kind, quantity and frequency of food intake. Similar factors also effect the regeneration time, that is, the time required to reattain normal pH value for the saliva. Depending upon the type of food, the pH value of the saliva, and therefore, that on tooth surfaces can drop to pH values 5.5 to 4.5, and in some situations, for example after ingestion of candies or other sweets, even lower pH values may prevail. pH values below 5.5 are generally considered undesirable because such strongly acidic conditions can bring about the result that the calcium compounds of the teeth are dissolved in the saliva. This in turn may lead to damage to the enamel, and eventually to dental caries. It may therefore be concluded that the greater the decline in the pH value on the tooth surface, the more time will be needed for regeneration of normal pH values and the greater the danger of dental corrosion and caries.
Furthermore, the thicker the film or plaque on tooth surfaces, the greater the danger of plaques on the tooth surfaces, acids produced through bacterial metabolism will require considerably more time to reach the surface of the film or plaque and antimicrobial agents require more time to effect bacterial decomposition so that there occur greater variations in the pH value on the tooth surfaces and in regeneration times.
Another problem which is nearly as important as the treatment and prevention of dental caries is the treatment and prevention of periodontitis at the stage of inflammation of the gingivae. An important aspect of the treatment of periodontitis is the reduction of tartar deposits deep in the pouches, which are associated with the loosening of the teeth symptomatic of this condition.
It has previously been disclosed that silver sulfadiazine possesses antibacterial properties and that silver sulfadiazine is useful in the topical treatment of burns. See for example, U.S. Pat. No. 3,761,590. It has also been previously disclosed that zinc sulfadiazine possesses antibacterial properties and is useful in burn therapy. See, for example, U.S. Pat. No. 4,049,802. Also there have been prior art disclosures of the use of zinc containing compounds or compositions in connection with dental care, including the reduction of dental plaque and dental caries. See, for example, U.S. Pat. No. 4,146,607, 4,082,841 and 4,152,418.
In accordance with the present invention it has been unexpectedly established that both the formation of dental plaque on the surfaces of teeth which is associated with dental caries and gingivitis or periodontitis can be eliminated or at least reduced to a substantial extent if silver and/or zinc sulfadiazine are added to a regularly used tooth or mouth caring composition such as a toothpaste, mouthwash, dental chewing gum or dental floss or tape.